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Timber Rattlesnakes vs. Lyme Disease

COLLEGE PARK, Md. - The scientific name of the timber rattlesnake, Crotalus horridus, is a sign of the fear and loathing this native North American viper has inspired for centuries. But new research by a team of University of Maryland biologists shows the timber rattlesnake indirectly benefits humans by keeping Lyme disease in check. The team's findings, presented today at the annual conference of the Ecological Society of America in Minneapolis, highlight the potential benefits of conserving all species – even those some people dislike.

Human cases of Lyme disease, a bacterial illness that can cause serious neurological problems if left untreated, are on the rise. The disease is spread by black-legged ticks, which feed on infected mice and other small mammals. Foxes and other mammal predators help control the disease by keeping small mammal populations in check. The decline of these mammal predators may be a factor in Lyme disease's prevalence among humans.

Timber rattlers are also top predators in Eastern forests, and their numbers are also falling, so former University of Maryland graduate student Edward Kabay wanted to know whether the rattlers also play a role in controlling Lyme disease.

Kabay used published studies of timber rattlers' diets at four Eastern forest sites to estimate the number of small mammals the snakes consume, and matched that with information on the average number of ticks each small mammal carried. The results showed that each timber rattler removed 2,500-4,500 ticks from each site annually.

Because not every human bitten by an infected tick develops Lyme disease, the team did not estimate how many people are spared from the disease because of the ecosystem service that timber rattlesnakes provide. But Kabay, who is now a science teacher at East Chapel Hill High School, and his research colleagues will talk about the implications of their findings at 4:20 p.m. today, Aug. 6, 2013, in Room 1011 of the Minneapolis Convention Center.

Timber rattlesnakes are endangered in six Eastern states and threatened in five more.

"Habitat loss, road kills, and people killing them out of fear are the big issues," said Kabay's advisor, associate biology professor Karen Lips. "They are non-aggressive and rarely bite unless provoked or stepped upon."

Lips directs the UMD graduate program in Sustainable Development and Conservation Biology. Her research focuses on the ecology, evolution, and conservation of amphibians, with interests at multiple scales (including populations, communities, and ecosystems), and with special interest in how amphibians are affected by emerging infectious disease and global change.

Lips is most widely known for her work studying, and trying to prevent, the world-wide loss of amphibian species that has been called the great amphibian extinction mystery. Read her personal, compelling account of 15 years of leading involvement in this effort in a May 15, 2013, Scientific American blog: "What If There Is No Happy Ending? Science Communication as a Path to Change." Follow her on Twitter @kwren88.